Shift Control Device for Straddle-Type Vehicle, and Straddle-Type Vehicle

ABSTRACT

A transmission mechanism is provide that can be interposed between a shift actuator and a shift shaft. The mechanism can include first and second coupling parts that can be coupled for movement relative to each other; a biasing mechanism that can be configured for urging the first and second coupling parts toward a neutral position; and a stopper mechanism that can be configured for stopping the relative movement of one of the first and second coupling parts when moved relatively from the neutral position against urging force of the biasing mechanism. When the shift actuator is stroked by a predetermined amount, a dog can be compulsorily disengaged as the first and second coupling parts are moved together by the stopper mechanism, and engaged as one of the first and second coupling parts moves relatively against the urging force, for allowing smooth shift change.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International ApplicationNo. PCT/JP2005/011803, filed Jun. 28, 2005, which claims priority toJapanese Application No. 2004-195632, filed Jul. 1, 2004, each of whichis hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally shift control devices forstraddle-type vehicles, and more specifically, to a shift control devicethat is operative to electrically control a transmission of thestraddle-type vehicle to change speeds.

2. Description of the Related Art

In some electric shift control devices, a conventional foot-operatedshift pedal is not used, but an electric motor (shift actuator) isactuated based on a speed change command signal that is output from ashift switch to rotate the shift shaft of a transmission for shiftchange.

In the case of shift change using a foot-operated shift pedal, repeatedshift operations may be required to complete the shift change if a dogin the transmission does not disengage or engage smoothly. However, withan electric shift control device, the shift change might not be made ifa dog does not disengage or engage smoothly.

In an attempt to address this problem related to electric shift controldevices, a feedback method has been proposed. According to this method,the angle of a shift cam is detected and fed back in order to adjust theoperation angle of the shift actuator for ensuring that the dog properlyand smoothly disengages and engages. Although beneficial, this methodcan be problematic due to slow shift speed and the complexity of thedevice.

This method is also problematic because in order to operate the shiftactuator at a predetermined angle in a predetermined period, the shiftactuator must keep operating even during abutment of the dog. Due to theabutment with the shift actuator, the dog may tend to rotate with theoperation of the shift actuator. Although it is possible to prevent thedog from rotating with the operation of the shift actuator, thisrequires the interposition of an actuation force transmission mechanism,such as a spring mechanism between the shift actuator and the shiftshaft. Further, if the load required to disengage the dog cannot beobtained with the spring, the dog cannot be disengaged. In addition, ifthe stroke amount of the shift actuator needs to be increased, the shiftspeed is made slower.

In view of the foregoing issues, Japanese Patent Document No.JP-B-3044498 discloses a technique for providing a lost motion mechanismconstituted of an elastic member between the electric motor and theshift shaft. This lost motion mechanism is interposed between a speedreduction gear mechanism (which is positioned between the output shaftand the shift drum shaft of the electric motor) and the shift shaft inorder to prevent the electric motor from being overloaded. Thus, insteadof being applied to the shift actuator, any overload is applied to theelastic member and results in elastic deformation of the elastic member.Therefore, when the shift shaft is rotationally driven by the resilientforce, the shift shaft can be rotationally driven smoothly, without theinfluence of the inertial mass of the speed reduction gear mechanism.Such a configuration tends to ensure smooth speed change shiftoperation.

Incidentally, albeit unrelated to electric shift control devices,Japanese Patent Document No. JP-Y-Sho 43-11555 discloses a technique forachieving smooth shift change using a foot-operated shift pedal. Thisreference teaches a coupling mechanism that is disconnected at a portionbetween the shift pedal and the shift shaft. Both the disconnected endsof the coupling mechanism are linked via an elastic member and have playequivalent to half the stroke of the shift pedal. With this structure,the dog can be disengaged with operation force of the shift pedaldirectly applied thereto, and can also be engaged always by the elasticforce of the elastic member. This configuration tends to ensure smoothshift change for foot-operated shift pedals.

Despite the beneficial shift control devices described in JapanesePatent Document Nos. JP-B-3044498 and JP-Y-Sho 43-11555, the elasticmembers are disposed in the engine case, for example, in the case of theelastic member of JP-B-3044498, between a reduced speed output gear,which is located at the final speed reduction end of the speed reductiongear mechanism, and the shift shaft. In the case of JP-Y-Sho 43-11555,the elastic member is disposed between a pedal shaft and a change arm.Hence, an existing structure cannot be utilized and high maintenance maybe required. Therefore, there is a need in the art for an actuationforce transmission mechanism that allows smooth shift change and iscompactly sized in order to mitigate any restriction on installationlocation and enable easy installation.

SUMMARY OF THE INVENTION

As described herein, several aspects of the present invention relate toa shift control device for a straddle-type vehicle for performing shiftcontrol. In accordance with various implementations, a shift actuatorcan be stroked by a predetermined amount to rotate a shift shaft, and adog can be engaged and disengaged by the rotation of the shift shaft.The embodiments described of the shift control device herein can thusprovide for a smooth-shifting straddle-type vehicle incorporating theactuation force transmission mechanism.

The shift control device can include a transmission mechanism comprisinga biasing mechanism and a stopper mechanism. The transmission mechanismcan also include a first coupling part and a second coupling partcoupled for movement relative to each other. The biasing mechanism canbe configured for urging the first and second coupling parts toward aneutral position. The stopper mechanism can be configured for stoppingthe relative movement of the first or second coupling part when thefirst or second coupling part is moved relatively from the neutralposition against urging force of the biasing mechanism. The transmissionmechanism can be disposed outside an engine case and be interposedbetween the shift actuator and the shift shaft.

In a preferred embodiment, the transmission mechanism can be arrangedsuch that, when resistive force acts against movement of thetransmission mechanism, one of the first and second coupling part movesrelatively against the urging force of the biasing mechanism until therespective coupling part is stopped by the stopper mechanism. Further,the first and second coupling parts can then move together.

In yet another embodiment, the biasing mechanism can include a firstbiasing member disposed in the first coupling part and a second biasingmember disposed in the second coupling part. The stopper mechanism caninclude a first stopper mechanism for stopping relative movement of thefirst coupling part and a second stopper mechanism for stopping relativemovement of the second coupling part.

Preferably, the urging force of the first biasing member and the urgingforce of the second biasing member are equal to each other.

In accordance with another embodiment, the first and second couplingparts can be coupled for movement relative to each other in slidingdirections (e.g., linearly).

In accordance with yet another embodiment, the biasing mechanism caninclude a compression spring.

In accordance with yet another embodiment, the first and second couplingparts can be coupled for movement relative to each other in rotatingdirections.

In accordance with yet another embodiment, the biasing mechanism caninclude a leaf-type spring. In a preferred embodiment, the leaf springhas an elongated rod-like shape (that is, configured substantially as aneedle).

In accordance with yet another embodiment, the transmission mechanismcan be disposed on the shift shaft.

In accordance with yet another embodiment, the transmission mechanismcan be disposed on a rotation axis of a gear of a speed reductionmechanism coupled to the shift actuator.

In accordance with yet another embodiment, the shift actuator can becoupled to the shift shaft via a coupling mechanism for transmittingactuation force of the shift actuator. In addition, the transmissionmechanism can be held by the coupling mechanism.

In accordance with yet another embodiment, the transmission mechanismcan be provided in a case held by the coupling mechanism.

In accordance with yet another embodiment, the shift actuator can becoupled to the shift shaft via a coupling mechanism for transmittingactuation force of the shift actuator; and the coupling mechanism is ofadjustable length.

Embodiments of the shift control device for a straddle-type vehicle cantherefore allow smooth shift change even when disengagement of the dogis difficult or dog abutment occurs during engagement of the dog.

Finally, embodiments of the transmission mechanism described herein canbe disposed outside an engine case that houses the shift shaft. In thisway, the transmission mechanism can be provided without the need tomodify the inside of the engine case and can be easily maintained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are schematic diagrams showing the basic structureof a shift control device for a straddle-type vehicle, which includes anactuation force transmission mechanism, configured according toembodiments of the present invention.

FIGS. 2(a) to 2(e) show how the transmission mechanism of FIG. 1(a) canoperate when a shift actuator is stroked by a predetermined amount inaccordance with an implementation of the present invention.

FIGS. 3(a) to 3(g) show a specific structure and operation of theactuation force transmission mechanism in accordance with an embodimentthe present invention.

FIG. 4 is a graph showing the rotational angle of a shift shaft versusthe stroke length of the shift actuator in accordance with an embodimentof the present invention.

FIG. 5 shows how a neutral position can be set using coil springs ofdifferent urging forces in accordance with an embodiment of the presentinvention.

FIG. 6 is a side view of a two-wheeled motor vehicle in accordance withan embodiment of the present invention.

FIG. 7 is a plan view of an engine provided with the shift actuator inaccordance with an embodiment of the present invention.

FIG. 8 is a side view of the engine provided with the shift actuator inaccordance with an embodiment of the present invention.

FIG. 9 is an exploded perspective view of a transmission mechanism inaccordance with an embodiment of the present invention.

FIG. 10 shows the developed shape of grooves in a shift cam inaccordance with an embodiment of the present invention.

FIG. 11 is a side view of the shift actuator in accordance with anembodiment of the present invention.

FIG. 12 is a perspective view of an actuation force transmissionmechanism in accordance with an embodiment of the present invention.

FIG. 13 is another perspective view of the actuation force transmissionmechanism in accordance with an embodiment of the present invention,viewed from a direction different from that illustrated in FIG. 12.

FIG. 14 is a front view of the actuation force transmission mechanism inaccordance with an embodiment of the present invention, viewed from thedirection of the arrow A in FIG. 12.

FIG. 15 is a right side view corresponding to FIG. 14.

FIG. 16 is a plan view corresponding to FIG. 14.

FIG. 17 is a block diagram showing an engine control unit in accordancewith an embodiment of the present invention.

FIG. 18 shows an actuation force transmission mechanism according to yetanother embodiment of the present invention in a normal state, in whichFIG. 18(a) is a plan view of an embodiment of the actuation forcetransmission mechanism, FIG. 18(b) is a sectional view taken along theline B-B of FIG. 18(a), and FIG. 18(c) is a sectional view taken alongthe line C-C of FIG. 18(a).

FIG. 19 shows the actuation force transmission mechanism according tothe another embodiment of the present invention in the shortened state,in which FIG. 19(a) is a plan view of the actuation force transmissionmechanism, and FIG. 19(b) is a sectional view corresponding to FIG.19(a).

FIG. 20 shows the actuation force transmission mechanism according tothe another embodiment of the present invention in an expanded state, inwhich FIG. 20(a) is a plan view of the actuation force transmissionmechanism, and FIG. 20(b) is a sectional view corresponding to FIG.20(a).

FIG. 21 shows the actuation force transmission mechanism according toanother embodiment of the present invention in a divided state.

FIG. 22 shows the structure of a stopper member in another embodiment ofthe present invention.

FIGS. 23(a) and 23(b) show the structure of the stopper member in stillanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawings, wherein the figures are provided forpurposes of illustrating preferred embodiments of the present inventionand not for purposes of limiting the same, FIGS. 1-3 illustrateembodiments of a shift control device for a straddle-type vehicle. Abasic description of the actuation force transmission mechanism will beprovided first, followed by a detailed description of specificstructures utilizable in accordance with embodiments of the presentinvention.

FIGS. 1(a) and 1(b) are conceptual diagrams showing the basic structureof an embodiment of the shift control device for a straddle-typevehicle.

FIG. 1(a) is a conceptual diagram showing a transmission mechanism 10interposed between a shift actuator and a shift shaft in the shiftcontrol device in accordance with an embodiment of the presentinvention. Normally, the shift actuator can be coupled to the shiftshaft through a coupling rod or the like. The shift actuator can bestroked by a predetermined amount to rotate the shift shaft. Therotation of the shift shaft can engage and disengage a dog to controlshift change. In an embodiment, the transmission mechanism 10 can bedisposed at an intermediate portion of the coupling rod.

As shown in the embodiment illustrated in FIG. 1(a), the transmissionmechanism 10 can include a first coupling part 11 a and a secondcoupling part 11 b coupled for movement relative to each other. Thetransmission mechanism 10 can also include a biasing mechanism 12 forurging the first and second coupling parts 11 a, 11 b toward a neutralposition. Finally, the transmission mechanism 10 can also include astopper mechanism 13 for stopping relative movement of the first orsecond coupling part 11 a, 11 b when they move relative to each otherfrom the neutral position against an urging force of the biasingmechanism 12.

Another embodiment of the transmission mechanism 10 shown in FIG. 1(b)has a structure similar to that shown in FIG. 1(a), but is provided witha biasing mechanism 12 and a stopper mechanism 13 for each of the firstand second coupling parts 11 a, 11 b. Thus, the first coupling part 11 acan be provided with a first biasing member 12 a and a first stoppermechanism 13 a for stopping relative movement of the first coupling part11 a. In like manner, the second coupling part 11 b can be provided witha second biasing member 12 b and a second stopper mechanism 13 b forstopping relative movement of the second coupling part 11 b. Asdiscussed below, the biasing mechanism can be a resilient componentvariously sized and configured to assist in the return the first andsecond coupling parts 11 a, 11 b to or from the neutral position.Further, the stopper can also be variously sized and configured toassist in limiting the movement of the first and second coupling parts11 a, 11 b. The operation of the actuation force transmission mechanism10 shown in FIG. 1(b) is similar to that of the actuation forcetransmission mechanism 10 shown in FIG. 1(a), and hence only the latteris described here.

According to implementations of the present invention, the operation ofthe above transmission mechanism 10 is now described with reference toFIGS. 2(a) to 2(e).

FIGS. 2(a) to 2(e) show how the transmission mechanism 10 can operatewhen the shift actuator is stroked by a predetermined amount.

FIG. 2(a) shows a state in which the first coupling part 11 a and thesecond coupling part 11 b are held at the neutral position of thetransmission mechanism 10 by the urging force of the biasing mechanism12. After the shift actuator is stroked by a predetermined amount and ashift up or a shift down is completed, the shift actuator can return toa predetermined position. If the first and second coupling parts 11 a,11 b deviate from the neutral position at that time, however, the dogcan become disengaged and may subsequently be engaged at deviatedpositions by the rotation of the shift shaft at the next shift up orshift down. This condition may hinder smooth shift change. However, theurging force of the biasing mechanism 12 can be preset such that thefirst and second coupling parts 11 a, 11 b can be prevented fromdeviating from the neutral position.

With reference still to FIGS. 2(a)-(e), when the shift actuator in thisstate is actuated in response to a gear change command signal and startsbeing stroked by a predetermined amount, an actuation force F1 in thedirection of the arrow (labeled F1) can be applied to the transmissionmechanism 10 from the shift actuator side (the right side of thedrawing) as shown in FIG. 2(a). At this time, when some resistive forceR1 (which will be described specifically later) acts against movement ofthe transmission mechanism 10 on the shift shaft side (the left side ofthe drawing) of the transmission mechanism 10, the biasing mechanism 12(e.g. a compression spring) can be compressed, and as a result, thefirst coupling part 11 a can move relatively from a neutral position, asshown in FIG. 2(a), to a position shown in FIG. 2(b). As also shown, thefirst coupling part 11 a can move relatively against the biasingmechanism 12 until the movement of the first coupling part 11 a isstopped by action of the stopper mechanism 13, as shown in FIG. 2(b).

When the movement of the first coupling part 11 a relative to the secondcoupling part 11 b is stopped, the first coupling part 11 a and thesecond coupling part 11 b can move together as shown in FIGS. 2(b)-(c).At this time, the transmission mechanism 10 can move in a “rigid” stateand can therefore be enabled to move against the resistive force R1 toeffectively rotate the shift shaft.

When the resistive force R1 is no longer applied against the movement ofthe transmission mechanism 10, as shown in FIG. 2(d), the urging forceof the biasing mechanism 12 can urge the first coupling part 11 a towardthe neutral position, and the transmission mechanism 10 can keep movingas the shift actuator is stroked.

Then, when some resistive force R2 (which will be described specificallylater) acts against the movement of the transmission mechanism 10 again,the biasing mechanism 12 can be compressed as shown in FIG. 2(e), and asa result, the first coupling part 11 a can move relatively against thebiasing mechanism 12 to a point before it is stopped by the stoppermechanism 13 in the same way as in FIG. 2(b). When the relative movementof the first coupling part 11 a is stopped, the second coupling part 11b can be urged by the biasing mechanism 12 against the resistive forceR2. Without the resistive force R2, the second coupling part 11 b can bemoved by the urging force of the biasing mechanism 12.

As described above, when some resistive force acts against movement ofthe transmission mechanism 10 in which the first coupling part 11 a andthe second coupling part 11 b are coupled to each other, the biasingmechanism 12 and the stopper mechanism 13 can work in conjunction witheach other to relatively move the first coupling part 11 a (or thesecond coupling part 11 b) for a certain period in order to relieve theresistive force. After the certain period, the first coupling part 11 aand the second coupling part 11 b can move together to allow theactuation force of the shift actuator to act directly on the shiftshaft.

The above description describes a typical example of the operation ofthe transmission mechanism 10. The operation of the transmissionmechanism 10 can vary depending on the magnitude and duration ofresistive force which acts on the transmission mechanism 10, the strokelength of the shift actuator, etc.

For example, in the case where the resistive force R1 is applied to thetransmission mechanism 10 of the above example for only a short period,the compression of the biasing mechanism 12 may not move the firstcoupling part 11 a far enough relative to the second coupling part 11 bto cause the first coupling part 11 a to be stopped by the stoppermechanism 13. Instead, the first coupling part 11 a can return towardthe neutral position when the resistive force R1 is no longer applied.

In the case where the shift actuator is stroked in the oppositedirection, the transmission mechanism 10 can basically perform the sameoperation as shown in FIGS. 2(a) to 2(e). In such as case, thetransmission mechanism 10 could have a symmetrical structure withrespect to the neutral position.

In the operation of the transmission mechanism 10 of the above example,the first coupling part 11 a and the second coupling part 11 b can becoupled so as to be movable relative to each other in slidingdirections. However, the first coupling part 11 a and the secondcoupling part 11 b can also be coupled so as to be movable relative toeach other in rotating directions.

The foregoing describes exemplary conceptual structures and operationsof embodiments of the transmission mechanism 10. Now, exemplary specificstructures and operations of embodiments of the transmission mechanism10 are described in association with actual engagement and disengagementof the dog with reference to FIGS. 3 and 4.

FIGS. 3(a) to 3(g) show exemplary operation of an embodiment of thetransmission mechanism 10 and exemplary operation of an embodiment of adog mechanism. FIG. 4 shows the rotational angle of the shift shaftversus the stroke length of the shift actuator, according to animplementation of the present invention. According to one embodiment,the transmission mechanism 10 can have first and second coupling partsthat each have an urging mechanism and a stopper mechanism. However, itsbasic operation is the same as a transmission mechanism with one biasingmechanism and one stopper mechanism.

The right side of FIG. 3(a) shows an embodiment of the transmissionmechanism 10 with the first coupling part 11 a and the second couplingpart 11 b held in the neutral position. The left side of FIG. 3(a) showsan embodiment of the dog mechanism with a dog 20 engaged with a gear 21.

As shown in FIG. 3(a), the first coupling part 11 a of the transmissionmechanism 10 can be inserted into an opening of, and slideably coupledto the second coupling part 11 b. A first coil spring 12 a can act as abiasing member, and along with a first stopper member 13 a, can bedisposed in an opening 16 a of the first coupling part 11 a. Likewise, asecond coil spring 12 b can act as a biasing member, and along with asecond stopper member 13 b, can be disposed in an opening 16 b of thesecond coupling part 11 b.

When a gear change command signal is input to the shift actuator in thisstate, the shift actuator can subsequently be stroked by a predeterminedamount. With reference now to FIG. 4, the shift shaft normally has“play” and can thus rotate by the play when the shift actuator is firststroked (represented by the diagonal line on the graph intermediatenumbers 1 and 2 on the horizontal axis of FIG. 4).

As the shift actuator is further stroked, disengagement of the dog canstart. The frictional force of the dog 20 in engagement with the gear 21can act as resistive force against the movement of the shift actuator asshown in FIG. 3(b). Thus, according to an implementation of the presentinvention, the transmission mechanism 10 interposed between the shiftactuator and the shift shaft can operate in such a way that the firstcoil spring 12 a disposed in the first coupling part 11 a can becomecompressed. As a result, the second coupling part 11 b can moverelatively from the neutral position.

The second coupling part 11 b can move relatively against the first coilspring 12 a until the first stopper mechanism 13 a comes in contact withthe sidewall of a support member 15 of the second coupling part 11 b.While the support member 15 abuts the first stopper mechanism 13 a, thefirst coupling part 11 a and the second coupling part 11 b are in a“rigid” state; the shift shaft does not rotate as the shift actuator isstroked during this stage of stroke (represented by the horizontal lineon the graph intermediate numbers 2 and 3 on the horizontal axis of FIG.4).

Furthermore, when the relative movement of the second coupling part 11 bis stopped, the first coupling part 11 a and the second coupling part 11b can move together as shown in FIG. 3(c). At this time, since thetransmission mechanism 10 moves in as it were a “rigid” state, theactuation force of the shift actuator is applied directly to the shiftshaft and exceeds the above-described frictional force so that the dog20 disengages from the gear 21 during this stage of stroke (representedby the diagonal line on the graph intermediate numbers 3 and 4 on thehorizontal axis of FIG. 4).

When the dog 20 is completely disengaged, frictional force of the dog 20with gear 21 no longer exists. Thus, the urging force of the first coilspring 12 a can then return the second coupling part 11 b toward theneutral position as shown in FIG. 3(d). After the dog 20 is disengaged,the shift shaft can rotate with almost no resistive force acting againstthe movement of the transmission mechanism 10 (represented by thediagonal line on the graph intermediate numbers 4 and 5 on thehorizontal axis of FIG. 4).

Then, as shown in FIG. 3(e), resistive force due to abutment of the dogacts against the movement of the shift actuator when the dog 20 engageswith a gear 22. Again, as shown in FIG. 3(f), the first coil spring 12 adisposed in the first coupling part 11 a can become compressed, and thesecond coupling part 11 b can then move relatively from the neutralposition. In the abutment of the dog 20, small urging force of the firstcoil spring 12 a acts on the dog 20, and allows the dog 20 to engagewith the gear 22 smoothly (represented by the horizontal line on thegraph intermediate numbers 5 and 6 on the horizontal axis of FIG. 4).Once the dog 20 is completely engaged with the gear 22, there no longerexists resistive force as shown in FIG. 3(g). Thus, the urging force ofthe first coil spring 12 a can return the second coupling part 11 btoward the neutral position.

Preferably, a gap can be provided so that the second coupling part 11 bwill move relatively not to be stopped by the first stopper mechanism 13a when the shift actuator is fully stroked and in the abutment of thedog, as shown in FIG. 3(f).

As described above, in an embodiment of the shift control device, thetransmission mechanism 10 can include a first coupling part 11 a and asecond coupling part 11 b, and can be coupled so as to provide movementrelative to each other. Further, the transmission mechanism 10 can beinterposed between the shift actuator and the shift shaft. When theshift actuator is stroked by a predetermined amount, the dog can becompulsorily disengaged as the first and second coupling parts 11 a, 11b are moved together by means of the stopper mechanism 13 (13 a, 13 b).Further, the dog can be engaged (in the abutment of the dog) as the oneof the first and second coupling part 11 a, 11 b is moved relativelyagainst the urging force of the biasing mechanism 12 (12 a, 12 b). Thiscan facilitate smooth shift change.

In the above description, the dog can be disengaged as the first andsecond coupling parts move together, such as when the frictional forceof the dog is great. However, it should be understood that the dog canbe successfully disengaged as one of the first and second coupling partsmoves relatively, such as when the frictional force of the dog is small.

According to an implementation, the transmission mechanism 10 describedabove has an independent structure and hence can be disposed outside anengine case which houses the shift shaft. In this way, the transmissionmechanism 10 can be provided without the need to modify the inside ofthe engine case and can be easily maintained.

In addition, the transmission mechanism 10 described above can be easilydisposed outside the engine case. For example, the transmissionmechanism 10 can be held by a coupling mechanism (a mechanism fortransmitting actuation force of the shift actuator to the shift shaft;for example, a coupling rod, a speed reduction mechanism, etc.) that canbe coupled to the shift actuator and the shift shaft. Further, thetransmission mechanism 10 described above can be effectively protectedfrom water and dust by disposing it in a case held by the couplingmechanism.

The shift actuator can be coupled to the shift shaft via a couplingmechanism of adjustable length for transmitting actuation force of theshift actuator.

In the case where the urging forces of the first and second coil springs12 a, 12 b are the same, the neutral position can be easily set.However, if the urging forces are different, the neutral position shouldbe set carefully. With reference now to FIG. 5, description will be madeof how the neutral position can be set using coil springs 12 a, 12 bthat have different urging forces.

As shown in FIG. 5(a), the free length of the first coil spring 12 a(spring constant: N1) provided in the first coupling part 11 a isdefined as L1, and the free length of the second coil spring 12 b(spring constant: N2) provided in the second coupling part 11 b isdefined as L2. Assuming that the first coupling part 11 a and the secondcoupling part 11 b of FIG. 5(b) are in the neutral position, and alsothe lengths of the first coil spring 12 a and the second coil spring 12b are respectively x and y, the following equations hold true:x+y+a=z  (1)N1×(L1−x)=N2×(L2−y)  (2)

The length x of the first coil spring 12 a and the length y of thesecond coil spring 12 b can be determined by solving these simultaneousequations (1), (2).

The basic structure of the shift control device for a straddle-typevehicle according to embodiments of the present invention has beendescribed above. Hereinafter, specific structures and operations ofvarious embodiments of the shift control device will be described indetail with reference to FIGS. 6 to 23.

FIGS. 6 to 17 show a specific structure of the shift control deviceaccording to an embodiment of the present invention. In FIG. 6,reference numeral 140 denotes a two-wheeled motor vehicle as a“straddle-type vehicle”, which can be provided with a front wheel 141 onits front side, a rear wheel 142 on its rear side, a fuel tank 144 inrear of handlebars 143, a seat 145 in rear of the fuel tank 144, and anengine 151 supported by a body frame below the fuel tank 144 and theseat 145.

A transmission (not shown) can be disposed in an engine case 152 for theengine 151. The transmission can have four to six speeds and adopts adog clutch. Power from a crankshaft of the engine 151 can be transmittedto a main axle, and then to a drive axle via gears and dogs forrespective speeds.

Speed change operation of the transmission can be achieved by a speedchange mechanism 155, an embodiment of which is shown in FIG. 9. Asshown in FIG. 9, the speed change mechanism 155 can include shift forks156 for regularly moving slide gears of the transmission, slidablymounted on a slide rod 157, and a rotatable shift cam 158 for slidingthe shift forks 156.

Cam grooves 158 a can be formed on the periphery of the shift cam 158.When developed, the cam grooves 158 a can be formed as shown in theexemplary embodiment of FIG. 10. The shift forks 156 can be adapted toslide along the cam grooves 158 a.

According to an embodiment, the shift cam 158 can rotate via a ratchetmechanism 160 as a shift shaft 159 rotates. The ratchet mechanism 160can be configured to provide a ratchet function for both forward andreverse directions to change one gear at a time. For example, theratchet mechanism 160 can rotate the shift cam 158 with constantintervals (such as by a constant angle) to move the shift forks 156regularly. A shift arm 161 of the ratchet mechanism 160 transmitsrotation of the shift shaft 159, and can also restrict the stroke ofshift shaft 159 in order to prevent the shift cam 158 from overrunning.A stopper plate 162 of the ratchet mechanism 160 can be utilized to keepthe shift cam 158 in specified positions.

The shift shaft 159 can move rotationally in a predetermined directionthrough a device such as described below.

With reference now to the embodiment illustrated in FIG. 7, a distal end159 a of the shift shaft 159 can project from the engine case 152 to theoutside of the engine, and can be provided with an actuation forcetransmission mechanism 164. The shift shaft 159 can be rotated bydriving force of the shift actuator 165 via the actuation forcetransmission mechanism 164.

As shown in FIGS. 7 and 8, the shift actuator 165 can be disposed on aside of the upper part of the engine case 152 along the longitudinaldirection of the vehicle. As shown in FIG. 11, the shift actuator 165can be provided with a worm gear 165 a at the distal end of its rotaryshaft. The worm gear 165 a can be configured to mesh with a pinion gear166. A coupling shaft 166 a can be provided eccentrically with respectto the center axis of the pinion gear 166.

As seen in FIG. 7, one end 167 a of a coupling rod 167 extendingvertically can be coupled to the coupling shaft 166 a for free rotation.Additionally, another end 167 b of the coupling rod 167 can be coupledto the actuation force transmission (conveyance) mechanism 164 as shownin FIG. 8.

According to another embodiment, the coupling rod 167 can be constitutedwith two halves. One of the halves can have a male-threaded end and theother halve can have a female-threaded end. In this regard, and the twohalves can be configured to be coupled to each other by screwing andthen fixing them with a nut. This structure can allow for the adjustmentof the distance between the shift actuator 165 and the shift shaft 159by loosening the nut, rotating one half of the coupling rod 167 toadjust its length, and then tightening the nut to complete theadjustment.

As shown in an embodiments of FIGS. 12 to 16, in the actuation forcetransmission mechanism 164, the other end 167 b of the coupling rod 167can be coupled to a rotary frame 170. In this regard, the rotary frame170 of the actuation force transmission mechanism 164 can be disposedaround the shift shaft 159 for free rotation relative to the shift shaft159. Additionally, the other end 167 b of the coupling rod 167 can becoupled to a coupling recess 170 a of the rotary frame 170 for freerotation. The rotary frame 170 can be provided with an actuation piece170 b that can be configured to project therefrom, such as by being bentfrom the rotary frame 170 or otherwise connected thereto. The actuationpiece 170 b can be inserted between two support bars 172 of a spring171, which functions as a biasing mechanism. Each bar preferably has athin elongated rod-like shape, similar to a pine needle. The two supportbars 172 can urge the actuation piece 170 b toward the neutral positionshown in FIGS. 13 and 15.

Also, in accordance with another implementation of the actuation forcetransmission mechanism 164 shown in FIGS. 12-16, a fixed lever 174 canbe fixed to the distal end 159 a of the shift shaft 159. As shown inFIGS. 13-16, the fixed lever 174 can be provided with apin-to-be-pressed 174 a projecting therefrom. The pin-to-be-pressed 174a can be inserted between the pair of support bars 172.

With this structure, when the rotary frame 170 is moved rotationally inan arbitrary direction from the neutral position, the actuation piece170 b can press one of the two support bars 172 while the other of thesupport bars 172 can press the pin-to-be-pressed 174 a. In such amanner, the shift shaft 159 can be moved rotationally in an arbitrarydirection by a predetermined amount at least due in part to the fixedlever 174. In addition, the shift shaft 159 can also be movedrotationally by the urging force of the support bars 172.

Furthermore, the rotary frame 170 can rotate against the urging force ofthe spring bars 171, 172 and move relative to the fixed lever 174. Suchmovement of the rotary frame 170 relative to the fixed lever 174 can beby a predetermined amount in a rotational direction, and then thepin-to-be-pressed 174 a of the fixed lever 174 can be contacted andpressed by one of a pair of stopper edges 170 c, 170 c of the rotaryframe 170. This contact can function as a “stopper means”. Thus, themovement of the rotary frame 170 relative to the fixed lever 174 in arotational direction can be stopped. In this regard, the rotationalforce of the rotary frame 170 can act directly on the fixed lever 174 sothat the shift shaft 159 moves rotationally together with the fixedlever 174.

Meanwhile, an engine control unit 210 for controlling the engine 151 canbe provided as shown in FIG. 17. In accordance with an implementation ofthe embodiment, various components can be connected to the enginecontrol unit 210; such components can include an engine speed sensor211, a vehicle speed sensor 212, a clutch actuator position sensor(potentiometric sensor) 213, a shift actuator position sensor 214, agear position sensor 215, an UP switch 216 for shifting up, and a DOWNswitch 217 for shifting down. Detected values and operation signals fromthese components can be input to the engine control unit 210. In apreferred embodiment, the UP switch 216 and the DOWN switch 217 can beprovided on the handlebars 143.

As also shown in FIG. 17, the engine control unit 210 can be connectedto a clutch actuator 218, the shift actuator 165, a gear positiondisplay section 219, an engine ignition section 220, and a fuelinjection device 221, which can be driven and controlled based on thesignals from the various sensors 211, etc.

The signals from the UP switch 216, the DOWN switch 217, the shiftactuator position sensor 214, the gear position sensor 215, etc., can beinput to the engine control unit 210, and control signals from theengine control unit 210 can be used to drive and control the shiftactuator 165.

Next, various functions of embodiments of the present invention will bedescribed.

In order to change speeds of the transmission, the UP switch 216 or theDOWN switch 217 can be provided on the handlebars 143. These switches216, 217 can be operated to actuate the shift actuator 165 in order torotate the worm gear 165 a in a predetermined direction by apredetermined amount.

The pinion gear 166, shown illustratively in FIG. 11, can then rotate ina predetermined direction. In addition, the coupling shaft 166 a, whichcan be disposed eccentrically with respect to the pinion gear 166, canmove rotationally so that the coupling rod 167 is pushed downward orpulled upward.

In addition, the rotary frame 170 can move rotationally in apredetermined direction via the coupling rod 167. This rotationalmovement can cause the actuation piece 170 b of the rotary frame 170 topress one of the two support bars 172. In turn, this can cause the otherof the support bars 172 to elastically press the pin-to-be-pressed 174 aof the fixed lever 174. The pressing of the support bars 172 against thepin-to-be-pressed 174 a can then cause the rotational movement of theshift shaft 159 in a predetermined direction via the fixed lever 174.

When the shift shaft 159 is moved rotationally in this way, the shiftcam 158 can move rotationally in a predetermined direction via theratchet mechanism 160. Further, the shift forks 156 can then be guidedby the cam grooves 158 a to slide in predetermined directions. The slidegears of the transmission can thus be moved, and the dog can bedisengaged while the dog for another is engaged.

When the dog is to be engaged, there are cases where the dog contactsanother dog due to bad timing and hence is not engaged immediately. Evenin such cases, the dogs can be subjected to comparatively small urgingforce of the two support bars 172 and hence may not abut against eachother with large force. Thus, the components can be protected fromdamage or the like. After that, the slide gears can move rotationallyslightly, and the urging force of the rotational movement can cause thedogs to be meshed with each other reliably.

According to an embodiment of the present invention, at the time whenthe two support bars 172 are elastically deformed and the rotary frame170 and the fixed lever 174 are moved relatively in a rotationaldirection by a predetermined amount, one of the stopper edges 170 c ofthe rotary frame 170 can contact the pin-to-be-pressed 174 a of thefixed lever 174. This can cause the rotary frame 170 and the fixed lever174 to move rotationally together. Thus, even when the dog is engagedand difficult to be disengaged due to residual torque, the dog can becompulsorily disengaged.

To put it in other words, with a simple modification of the structure,the dog can be disengaged and engaged reliably and easily withoutprecise control, even in the case where the shift operation is performednot manually, but mechanically using the shift actuator 165.

According to another embodiment, the actuation force transmissionmechanism 164 can be disposed on the axis of the shift shaft 159, asshown in FIG. 8, thereby achieving a compact structure. The actuationforce transmission mechanism 164 can also be disposed outside the engine151, and can nevertheless be protected from water and dust easily byproviding a case 192 for covering it.

In accordance with another embodiment, the actuation force transmissionmechanism 164 can be disposed on the axis of a gear shaft 190 of adamping mechanism 191, and be coupled to the shift actuator 165 as shownin FIG. 8. Such an embodiment can be an alternative to coupling theactuation force transmission mechanism 164 on the axis of the shiftshaft 159.

Next, FIGS. 18 to 21 show another specific structure of the shiftcontrol device in accordance with another embodiment of the presentinvention. The structure to be described here can be different from theabove-described structure in respect to an actuation force transmissionmechanism 177.

That is, while the above-described actuation force transmissionmechanism 164 drives rotationally, the actuation force transmissionmechanism 177 to be described here can drive linearly. The actuationforce transmission mechanism 177 can be provided in place of thecoupling rod 167 in the above-described structure. Further, it iscontemplated that the actuation force transmission mechanism 164 may ormay not be provided in the such an embodiment.

As shown in the embodiments illustrated in FIGS. 18 to 21, the actuationforce transmission mechanism 177 can also be provided with first andsecond coupling parts 179, 180 slidably movable relative to each otherin linear directions. In such an embodiment, a coil spring 181, which isused as an “urging means,” and a stopper member 182 can be disposedbetween the first and second coupling parts 179, 180.

As shown in the embodiment of FIG. 21, the first coupling part 179 caninclude a base part 179 a, and a pair of plate parts 179 b, which can befixed to the base part 179 a with a constant interval. In accordancewith an implementation of such an embodiment, the two plate parts 179 bcan be formed with an opening 179 c where the coil spring 181 and thestopper member 182 are disposed. Further, and the two plate parts 179 bcan also include a coming-off prevention piece 179 d for preventing thecoil spring 181 and the stopper member 182 from coming off.

Also as shown in FIG. 21, the second coupling part 180 can include abase part 180 a, and a single plate part 180 b fixed to the base part180 a. The single plate part 180 b can be inserted between the pair ofplate parts 179 b of the first coupling part 179. The plate part 180 bcan also be formed with an opening 180 c generally of the same size asthe opening 179 c of the plate parts 179 b of the first coupling part179.

The coil spring 181 can be accommodated in the openings 179 c, 180 c ofthe respective plate parts 179 b, 180 b. Further, the columnar stoppermember 182 can be disposed inside the coil spring 181. A support shaft183 can be slidably inserted through the stopper member 182, anddisposed between the plate parts 179 b.

With this structure, to shift down, for example, the shift actuator 165can be driven to move the first and second coupling parts 179, 180 ofthe actuation force transmission mechanism 177 in compressingdirections. The coil spring 181 can be compressed against its urgingforce from the state shown in FIG. 18 to the state shown in FIG. 19.This urging force can rotate the shift shaft 159 to allow engagement ordisengagement of the dog.

When the dog is to be engaged, there are cases where the dog contactsanother dog due to bad timing and hence is not engaged immediately. Evenin such cases, the dogs can be subjected to comparatively small urgingforce of the coil spring 181 and hence may not abut against each otherwith large force. Thus, the components can be protected from damage orthe like. After that, the slide gears can move rotationally slightly,and the urging force of the rotational movement can cause the dogs to bemeshed with each other reliably.

As the coil spring 181 is elastically deformed and compressed, theopening 179 c of the plate parts 179 b and the opening 180 c of theplate part 180 b can be displaced from each other. At the time when thefirst and second coupling parts 179, 180 have moved relatively by apredetermined amount in linear directions, the width of an openingcommon to the displaced openings 179 c, 180 c can become coincident withthe width of the stopper member 182. This can stop the relative movementof the first and second coupling parts 179, 180, and cause the first andsecond coupling parts 179, 180 to move rotationally together. Thus, evenwhen the dog is engaged and difficult to be disengaged due to residualtorque, the dog can be compulsorily disengaged.

On the other hand, to shift up, for example, the shift actuator 165 canbe driven to relatively move the first and second coupling parts 179,180 in separating directions. Then, the opening 179 c of the plate parts179 b and the opening 180 c of the plate part 180 b can be displacedfrom the generally coincident position, and the coil spring 181 can becompressed. The urging force of the coil spring 181 can tend to ensureengagement of the dog as described above.

Further from this state, as the coil spring 181 is elastically deformed,the opening 179 c of the plate parts 179 b and the opening 180 c of theplate part 180 b can be displaced from each other. At the time when thefirst and second coupling parts 179, 180 have moved relatively by apredetermined amount in separating directions, the width of an openingcommon to the displaced openings 179 c, 180 c can become coincident withthe width of the stopper member 182. This can stop the relative movementof the first and second coupling parts 179, 180, and cause the first andsecond coupling parts 179, 180 to move rotationally together. Thus, evenwhen the dog is engaged and difficult to be disengaged due to residualtorque, the dog can be compulsorily disengaged.

It is contemplated that the first coupling part 179, the second couplingpart 180, and the stopper member 182 can be formed in variousconfigurations. Some exemplary embodiments are shown in FIGS. 22, 23(a)and 23(b).

In the example shown in FIG. 22, the second coupling part 180 can beconstituted of a rod, and the first coupling part 179 can be constitutedof a cylindrical member for accommodating a part of the rod. The coilspring 181, utilizable as an urging means, can be disposed between thefirst coupling part 179 (shown as a cylindrical member) and the secondcoupling part 180 (shown as a rod). A sidewall 182 a inside the firstcoupling part 179 and a step 182 b can be provided on the inner surfaceof the first coupling part 179 to respectively serve as stopper memberswhen the second coupling part 180 moves relative to the first couplingpart 179.

For example, when the second coupling part 180 moves relative to thefirst coupling part 179 toward the right side of FIG. 22, the coilspring 181 can be compressed by a circlip 190 b embedded in a portion ofthe first coupling part 179. The second coupling part 180 can moverelatively until its distal end contacts the sidewall 182 a (utilizableas a stopper member) inside the first coupling part 179.

Also, when the second coupling part 180 moves relative to the firstcoupling part 179 toward the left side of FIG. 22, the coil spring 181can be compressed by a circlip 190 a embedded in a portion of the firstcoupling part 179. The second coupling part 180 can move relativelyuntil the circlip 190 b embedded in a portion of the first coupling part179 contacts the step (stopper member) 182 b provided on the innersurface of the first coupling part 179.

The rod and the cylindrical member constituting the first coupling part179 and the second coupling part 180 can be of a circular, rectangularor any other shape as long as the cylindrical member can accommodate therod. The rod can have portions of different diameters, and a portion ofa large diameter may be used as a part contacted by the spring.

In addition, the cylindrical member can be constituted with pluralmembers having inner and outer surfaces. For example, the cylindricalmember can be constituted with plural semi-cylindrical members dividedalong the linear direction of the rod.

As illustrated in the example shown in FIG. 23(a), the distal end of thefirst coupling part 179 can be bent back and inserted into an opening ofthe second coupling part 180. Sidewalls 182 a, 182 b of the opening canbe used as stopper members. In the example shown in FIG. 23(b), a coilspring 181 is provided in an opening defined by the first coupling part179 and the second coupling part 180. A projection 182 a formed on thefirst coupling part 179 and a recess 182 b formed in the second couplingpart 180 can be fitted to each other to serve as stopper members.

The shift control device in embodiments of the present invention can bemounted on a two-wheeled motor vehicle, as shown in FIG. 6, in order toallow smooth shift change when the two-wheeled motor vehicle is running.

The term “two-wheeled motor vehicle” used herein can include motorcyclessuch as motorized bicycles (motorbikes) and scooters, and refersspecifically to vehicles whose turning can include tilting of thevehicle body. Thus, a vehicle having two or more front wheels and/or twoor more rear wheels and hence having a total of at least three wheels,can also be included in the “two-wheeled motor vehicle”. The embodimentsof the present invention are not limited to use in two-wheeled motorvehicles, but may also be applied to other vehicles which can takeadvantage of the effect of embodiments of the present invention.Examples of such vehicles include the so-called straddle-type vehiclesother than two-wheeled motor vehicles, such as four-wheeled buggies (allterrain vehicles (ATVs)) and snowmobiles.

Further, the “shift actuator” can be of an electric or hydraulic type.Instead of needle-like spring or coil spring, the biasing mechanism caninclude another type of spring, or an elastic member, such as rubber andresin.

When embodiments of the present invention are to be applied to actualstraddle-type vehicles, specific implementations should be examined froma comprehensive viewpoint which allows for each and every requirement inorder to produce an excellent effect such as described above.

Further, such implementations preferably facilitate easy installationand maintenance of embodiments of the shift control device which can beused for a straddle-type vehicle, utilizing an existing structure.

Although the embodiments of the present invention have been disclosed inthe context of certain preferred embodiments and examples, it will beunderstood by those skilled in the art that the teachings herein extendbeyond the specifically disclosed embodiments to other alternativeembodiments and/or uses of the embodiments of the present invention andobvious modifications and equivalents thereof. In addition, whileseveral variations of the embodiments have been shown and described indetail, other modifications, which are within the scope of theseembodiments, will be readily apparent to those of skill in the art basedupon this disclosure. It is also contemplated that various combinationor sub-combinations of the specific features and aspects of theembodiments may be made and still fall within the scope of theteachings. It should be understood that various features and aspects ofthe disclosed embodiments can be combined with or substituted for oneanother in order to form varying modes of the disclosed embodiments.Thus, it is intended that the scope of at least some of the embodimentsherein disclosed should not be limited by the particular disclosedembodiments described above.

1-12. (canceled)
 13. A straddle-type vehicle comprising: an engine casecontaining at least a portion of an engine; a speed-changingtransmission selectively driven by the engine, the speed-changingtransmission including a shift shaft and a dog; a shift actuator; and ashift control device for performing shift control of the speed-changingtransmission, the shift control device including a shift actuator and anactuation force transmission mechanism, the shift actuator beingconfigured to be stroked by a predetermined amount to move the shiftshaft and a dog into and out of engagement, the actuation forcetransmission mechanism being disposed outside the engine case and beinginterposed between the shift actuator and the shift shaft, and theactuation force mechanism including: first and second coupling partsbeing sized and configured to be coupled together to provide movementrelative to each other; a biasing mechanism for urging the first andsecond coupling parts toward a neutral position; and a stopper mechanismfor stopping the relative movement of the first and second coupling partwhen one of the first and second coupling parts is moved relatively fromthe neutral position against urging force of the biasing mechanism. 14.The straddle-type vehicle according to claim 13, wherein thetransmission mechanism is arranged such that, when a resistive forceacts against the movement of the transmission mechanism, the firstcoupling part moves relative to the second coupling part against theurging force of the biasing mechanism until the first coupling part isstopped by the stopper mechanism, and wherein in response to acontinuing resistive force, the first and second coupling parts movingtogether upon the first coupling part being stopped by the stoppermechanism.
 15. The straddle-type vehicle according to claim 13, whereinthe first and second coupling parts are coupled so as to slide relativeto each other.
 16. The straddle-type vehicle according to claim 15,wherein the biasing mechanism includes a compression spring.
 17. Thestraddle-type vehicle according to claim 13, wherein the first andsecond coupling parts are coupled for at least rotational movementrelative to each other.
 18. The straddle-type vehicle according to claim17, wherein the biasing mechanism includes a leaf-type spring having anelongated, rod-like shape.
 19. The straddle-type vehicle according toclaim 17, wherein the actuation force transmission mechanism is disposedon the shift shaft.
 20. The straddle-type vehicle according to claim 19,wherein the actuation force transmission mechanism is disposed on a gearshaft of a speed reduction mechanism coupled to the shift actuator. 21.The straddle-type vehicle according to claim 13, wherein the shiftactuator is coupled to the shift shaft via a coupling mechanism fortransmitting actuation force of the shift actuator to the shift shaft,the actuation force transmission mechanism is held by the couplingmechanism.
 22. The straddle-type vehicle according to claim 21, whereinthe transmission mechanism is provided in a case held by the couplingmechanism.
 23. The straddle-type vehicle according to claim 13, whereinthe shift actuator is coupled to the shift shaft via a couplingmechanism for transmitting actuation force of the shift actuator; thecoupling mechanism being of adjustable length.